Impulsive excitation of squeezed phonons in single crystal germanium by an x-ray laser
In this Letter, we present the experimental observation of squeezed phonon generation in semiconductor germanium (Ge) induced by x-ray excitation. Prior x-ray pump, x-ray probe studies reported coherent longitudinal acoustic phonon generation in insulating oxides like strontium titanate and potassium tantalate. In contrast, such signals were not observed in semiconductors likely due to limited signal-to-noise ratio. Now, with an improved experimental setup, we observe a phonon response in single-crystal germanium. Utilizing x-ray split-delay optics with enhanced stability, we extract the phonon dispersion relation, which shows strong agreement with the calculated transverse acoustic phonon mode. Our results reveal that responses to x-ray excitations in semiconductors are of a similar nature to optical excitations. This suggests that the initial response to x-ray core–hole excitations rapidly diffuses to a non-local excitation, similar to what is observed with optical laser valence excitation on a femtosecond timescale.
Authors
- David A. Reis (ORCID: https://orcid.org/0000-0002-1576-7533)
- Mike Dunne (ORCID: https://orcid.org/0000-0002-4978-5166)
- Sanghoon Song (ORCID: https://orcid.org/0000-0003-3493-1850)
- Takahiro Sato (ORCID: https://orcid.org/0000-0003-2202-0910)
- Yanwen Sun (ORCID: https://orcid.org/0000-0001-5926-6565)
- P. H. Fuoss (ORCID: https://orcid.org/0000-0002-3714-7239)
- Chance Ornelas-Skarin
- Nan Wang (ORCID: https://orcid.org/0000-0002-3938-2339)
- Peihao Sun (ORCID: https://orcid.org/0000-0002-3608-1557)
- Dillon F. Hanlon (ORCID: https://orcid.org/0000-0002-8926-3231)
- Diling Zhu (ORCID: https://orcid.org/0009-0001-4941-9799)
- Baochen She (ORCID: https://orcid.org/0000-0001-8696-4588)
- Mariano Trigo (ORCID: https://orcid.org/0000-0003-4655-188X)
- Samuel W. Teitelbaum (ORCID: https://orcid.org/0000-0002-0812-9832)
- Mark Sutton (ORCID: https://orcid.org/0000-0001-6390-1197)
- Haoyuan Li (ORCID: https://orcid.org/0000-0003-1845-3748)
- Yijing Huang (ORCID: https://orcid.org/0000-0002-5453-7722)
- Jerome Hastings (ORCID: https://orcid.org/0000-0002-3577-9857)
Institutions
- University of Padua (IT)
- University of Illinois Urbana-Champaign (US)
- SLAC National Accelerator Laboratory (US)
- Linac Coherent Light Source (US)
- McGill University (CA)
- Arizona State University (US)
- Stanford University (US)
Publication Details
- Journal
- Applied Physics Letters
- Published
- 2025-06-02
- DOI
- https://doi.org/10.1063/5.0269800
- Primary Topic
- Force Microscopy Techniques and Applications
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Basic Energy Sciences
- Chemical Sciences, Geosciences, and Biosciences Division